This invention relates to the analysis of objects, including living tissue, by observing the perturbation of interference fringes between two interfering coherent beams of radiation in the object space.
Instruments for the non-invasive analysis of the interiors of bodies, particularly biological tissue, are well known. By biologic tissue is meant living or dead tissue and the like. For example, x-ray apparatus is commonly used for the examination of both living tissue and inert materials. The use of x-rays for examination of living tissue, particularly human beings, is hazardous because x-rays are ionizing radiation. Therefore, the use of x-ray examination is limited and the resolution which can be obtained through x-ray examination is limited because of dosage considerations.
The use of radioactive material is also fairly common for the examination of living tissue where the material is injected or ingested or otherwise applied to the living tissue. The tissue is then scanned to determine the concentation pattern of the radioactive material. The use of such diagnostic techniques again involves the use of ionizing radiation and the use and resolution obtained by the measurement is limited.
Many other systems are known for the non-invasive testing of human tissues, such as nuclear magnetic resonance techniques (NMR). Nuclear magnetic resonance techniques are in growing use but the apparatus is extremely expensive and requires very long exposure times, for example 8-10 seconds, during which a patient can not move. Furthermore, the use of NMR equipment requires the patient to be placed in a long tunnel defining the magnet which has adverse psychological attributes.
Many other non-invasive examination mechanisms including those employing ultrasound are also known, each having well known disadvantages.